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That's impressive. It's close to the energy density of fuel oil. Or did I calculate that wrong?
Earlier quoted context omitted.
Can store a lot more heat by volume. Water has other bad properties. The higher the temperature the higher the pressure.
> [Sand] Can store a lot more heat by volume. A quick caveat/clarification: It's only true if you're pushing the system over the 100°C mark. Otherwise a volume of liquid water--with its greater latent heat-capacity--will outclass the same volume of sand. Water's heat-capacity is 4.186 J/g°C, while estimates for sand run towards ~0.830 J/g°C. If we also assume the sand is 1.6x denser, then our below-boiling water stil…
This is great technology, simple and effective. I’ve spent many hours reverse engineering to see how effective and expensive it might be. I’ve found it’s very cost effective but heat can be hard to calculate. i like that they did a prototype. i think i’ll do one at some point. for an individual house it makes more sense to improve my insulation but i think ill still build a small version for fun.
IceBear went out of business with the opposite tech: tanks of water storing the cold generated from excess AC cycles. Cheap electricity can make cold, and then a fan can convert the cold water into cold air during peak hours when electricity was costlier. Fans still took electricity to run, but it'd only be a few hundred watts to run air-conditioning rather than kilowatts of power.
Then again, the competition is general purpose batteries which can be used all year and probably require less maintenance.
This new sand battery is expected to stand 13 m (42.7 ft) tall and 15 m (49.2 ft) wide, providing an output power of 1 MW and a capacity of 100 MWh. That's impressive. It's close to the energy density of fuel oil. Or did I calculate that wrong?
It's still pretty good though.
The article doesn't mention the costs or complexity in building each unit but definitely implies it's cheaper than storing it batteries, which makes sense if it's essentially a heating element buried in sand.
Wonder what the smallest viable size would be, could you have one for each street / block of flats? One of the comments mentions burying them for better insulation which I'm assuming they didn't want to do just for the prototypes?
It isn’t a totally new concept, in CSP (concentrated solar power) plants, a molten salt is used to store the heat as well.
CSP stores heat as a means to produce electricity, the PNE sand battery stores heat as a means to provide heat. CSP's molten salt was heated by pumping it through (solar) heated pipes, which meant it had to have the correct fluid properties etc. The PNE sand is heated in-place via electricity which means it can be basically any old crap, as long as it's inert at 600 degrees or less.
In other words, CSP differs drastically by the energy input method, the energy output method, and the composition and requirements of the storage medium.
Basically all of the PNE tech is centuries old, the point is that together in this specific configuration they're an incredibly cheap heat storage medium - resistive heating, insulation, sand, all cheap.
It isn’t a totally new concept, in CSP (concentrated solar power) plants, a molten salt is used to store the heat as well.
novelty is secondary to implementation
In 2012 Vast Solar commenced its 1.2 MW Performance Validation Project which was supported by funding from the then Australian Solar Institute.
This CST project was completed on 22 October 2019.
Scaled up second stage is being built out now (2024):
Vast said on Friday that it has partnered up with global design and manufacturing firm Contratos y Diseños Industriales (CYD) to take the next step forward on its VS1 project, the 30MW/288MWh plant in South Australia.
I'm curious about "why sand", is it better at holding heat than say water?
That means that the hot middle of a sand pile stays hot, instead of advecting to the outside, where it cools by conduction.
Earlier quoted context omitted.
> [Sand] Can store a lot more heat by volume. A quick caveat/clarification: It's only true if you're pushing the system over the 100°C mark. Otherwise a volume of liquid water--with its greater latent heat-capacity--will outclass the same volume of sand. Water's heat-capacity is 4.186 J/g°C, while estimates for sand run towards ~0.830 J/g°C. If we also assume the sand is 1.6x denser, then our below-boiling water stil…
I think the original plan was to convert the heat back into electricity with a turbine. So the higher temperature of sand would greatly improve thermodynamic efficiency.
Is that just speculation or did you read it somewhere? IIRC the original motivation of PNE was a bunch of engineers at uni speculating on how to build the perfect building for engineers, and making it self-sufficient would require handling its own heating, which they originally thought would be best done with a big hot-water tank to store the heat. No turbine was suggested, IIRC.
I'm curious about "why sand", is it better at holding heat than say water?
It's more effective volume wise. I did the math, some time ago here are the rough numbers. Sand has way less heat capacity then water per kg (about half). Water can be heated to 95C with standard unpressurized vessel. Sand in this application is heated to 600C. Sand is denser then water (kg/m3). For the same heat energy stored this comes out to about 2.5x more volume of water(95C) compared to sand(600C). Water and Sa…
So yes, the volume of 95C water would be much greater than that of 600C sand, but if volume wasn't an issue you could do it much more efficiently. Alternatively, you could use battery storage for just the electrical capacity required and not the (much higher) thermal capacity which may be more cost effective when you look at the conversion.
[1] https://www.sciencedirect.com/science/article/abs/pii/S03605...